1. Field of the Invention
The present invention relates to a mounting structure for a thermostat to control a flow of coolant in a cooling system of an internal combustion engine.
2. Description of Background Art
There is already proposed a mounting structure for an embedded thermostat, e.g., see JP-A No. 39433/2002 (second embodiment). According to this structure, the thermostat is placed in an embedding hole that is formed across a coolant channel of a casing. A cover member covers the embedding hole via a rubber seal and fixes the thermostat.
Referring now to FIG. 17, the mounting structure for the embedded thermostat disclosed in the second embodiment of JP-A No. 39433/2002 provides an embedding hole 03 that is formed across a coolant channel 02 in a casing 01. A thermostat 07 is placed in the embedding hole 03. A cover member 05 covers the embedding hole 03 via a rubber seal 04 and fixes the thermostat 07.
The thermostat 07 has an entry aperture 08a and an exit aperture 08b on a surrounding wall of a cylindrical valve body 08. A valving element 09 advances and retracts to open and close the apertures 08a and 08b. The thermostat 07 is placed in the embedding hole 03 so that both apertures 08a and 08b face to the coolant channel 02 in the casing 01.
A by-pass aperture 08c is provided below the exit aperture 08b to connect an inside space of the valve body 08 with the coolant channel 02. When the valving element 09 advances and retracts due to thermal expansion of wax 010, the exit aperture 08b and the by-pass aperture 08c are selectively opened.
The thermostat 07 is surrounded with an O-ring 011 that partitions an outer peripheral surface of the valve body 08 into a side of the entry aperture 08a and a side of the exit aperture 08b. 
The cover member 05 has a by-pass channel 06 and is embedded with the rubber seal 04 in a circular groove. The cover member 05 is attached to the casing 01 via the rubber seal 04 so as to cover the embedding hole of the casing engaged with the thermostat 07.
The rubber seal 04 is pressed to an aperture end of the embedding hole in the casing and over to an aperture end of the cylindrical valve body 08 to fix the thermostat 07.
Accordingly, the O-ring 011 allows the outside space of the valve body 08 of the thermostat 07 to divide the inside of the embedding hole 03 of the casing 01 into halves, i.e., influx and efflux sides. The rubber seal 04 divides the valve body 08 into inside and outside spaces inside the embedding hole 03 of the casing 01.
The above-mentioned conventional structure has an advantage of compactly configuring a thermostat unit. However, the thermostat 07 is supported by the O-ring 011 in a floating manner. No positioning structure is provided to the rubber seal 04 and the casing 01. This causes slight misalignment to the thermostat 07 after assembly.